Field of the Invention
The present invention relates to wireless communication and, more particularly, to a method and apparatus for reporting channel state information in a wireless communication system.
Related Art
3rd generation partnership project (3GPP) Long Term Evolution (LTE), that is, an improvement of a Universal Mobile Telecommunication System (UMTS), is introduced as the 3GPP release 8. The 3GPP LTE uses Orthogonal Frequency Division Multiple Access (OFDMA) in downlink, and uses Single Carrier-Frequency Division Multiple Access (SC-FDMA) in uplink. The 3GPP LTE employs Multiple Input Multiple Output (MIMO) having up to four antennas. In recent years, there is an ongoing discussion on 3GPP LTE-Advanced (LTE-A) that is an evolution of the 3GPP LTE.
As disclosed in 3GPP TS 36.211 V8.7.0 (2009-05) “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8),” in 3GPP LTE/LTE-A, physical channels may be divided into a physical downlink shared channel (PDSCH) and a physical downlink control channel (PDCCH), that is, downlink channels, and a physical uplink shared channel (PUSCH) and a physical uplink control channel (PUCCH), that is, uplink channels.
Conventional 3GPP LTE provides a Cell-specific Reference Signal (CRS) used to estimate channel state information. However, the CRS is transmitted in all the subframes over the entire system band. Accordingly, a scheme for not sending the CRS or sending the CRS in limited resources is being discussed in order to reduce overhead attributable to the transmission of the CRS in all the subframes over the entire system band.